The catalog pg_class catalogs
tables and most everything else that has columns or is otherwise
similar to a table. This includes indexes (but see also
pg_index), sequences, views,
composite types, and some kinds of special relation; see
relkind. Below, when we mean all of
these kinds of objects we speak of "relations". Not all columns are meaningful for
all relation types.

True if this is a table and it has (or recently had)
any indexes. This is set by CREATE
INDEX, but not cleared immediately by DROP INDEX. VACUUM clears relhasindex if it finds the table has
no indexes.

relisshared

bool

True if this table is shared across all databases in
the cluster. Only certain system catalogs (such as
pg_database) are shared.